1ht3

From Proteopedia

Revision as of 14:41, 20 November 2007

MERCURY INDUCED MODIFICATIONS IN THE STEREOCHEMISTRY OF THE ACTIVE SITE THROUGH CYS-73 IN A SERINE PROTEASE: CRYSTAL STRUCTURE OF THE COMPLEX OF A PARTIALLY MODIFIED PROTEINASE K WITH MERCURY AT 1.8 A RESOLUTION

Overview

Proteinese K (PK) isolated from Tritirachium album Limber was crystallized, with HgCl2 in excess, under microgravity conditions. The intensity data, were collected at 4 degrees C to 1.8 A resolution and the final R-factor, after refinement for all the reflections was 0.164. Mercury has been found, at two sites with partial occupancies (0.4 and 0.6) which are at distances, of 2.48 A and 2.58 A respectively from Cys-73 Sgamma. The Cys-73 in the, enzyme structure is located close to the active site residue, His-69. This, region is completely buried and is not accessible to the solvent. It is, rather tightly packed. Therefore, the binding of mercury distorts the, stereochemistry of the neighbouring residues including those belonging to, the catalytic triad. As a result of this, the Ogamma of Ser-224 is, displaced by 0.6 A which causes the inactivation of proteinase K by, increasing the H-bond distance to 3.7 A between Ser-224 Ogamma and His-69, Nepsilon2.

About this Structure

1HT3 is a Single protein structure of sequence from Engyodontium album with HG and CA as ligands. Active as Peptidase K, with EC number 3.4.21.64 Full crystallographic information is available from OCA.

Reference

Mercury induced modifications in the stereochemistry of the active site through Cys-73 in a serine protease--crystal structure of the complex of a partially modified proteinase K with mercury at 1.8 A resolution., Gourinath S, Degenhardt M, Eschenburg S, Moore K, Delucas LJ, Betzel C, Singh TP, Indian J Biochem Biophys. 2001 Oct;38(5):298-302. PMID:11886076

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